Materials for electronic devices

ABSTRACT

The present application relates to a material comprising a monoarylamine of a formula (A) and a p-dopant of a defined formula. The present application further relates to the use of said material in an organic layer of an electronic device, the device preferably being an organic electroluminescent device (OLED).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application (under 35 U.S.C. § 371) of PCT/EP2015/001940, filed Oct. 2, 2015, which claims benefit of European Application Nos. 14003629.4, filed Oct. 24, 2014, and 15180257.6, filed Aug. 7, 2015, all of which are incorporated herein by reference in their entirety.

The present application relates to a material comprising a monoarylamine of a defined formula (A) and a complex of bismuth. The present application further relates to the use of said material in an organic layer of an electronic device, the device preferably being an organic electroluminescent device (OLED).

The term “comprising” is understood in the context of this application to mean that further constituents or steps may be present. The indefinite article “a” does not exclude the plural.

Electronic devices in the context of this application are understood to mean what are called organic electronic devices, which contain organic semiconductor materials as functional materials.

The structure of OLEDs in which organic compounds are used as functional materials is described, for example, in U.S. Pat. Nos. 4,539,507, 5,151,629, EP 0676461 and WO 98/27136. In general, the term OLEDs is understood to mean electronic devices which have one or more layers comprising organic compounds and emit light on application of electrical voltage.

A great influence on the performance data of electronic devices is possessed by layers having a hole-transporting function (hole-transporting layers), for example hole injection layers, hole transport layers and electron blocker layers.

The prior art discloses use of monoarylamines as materials for hole-transporting layers. Such monoarylamines are described, for example, in JP 1995/053955, WO 2006/123667, JP 2010/222268, WO 2012/034627, WO 2013/120577, WO 2014/015938 and WO 2014/015935.

In addition, the prior art discloses use of p-dopants in combination with hole transport materials in hole-transporting layers of OLEDs. A p-dopant is understood here to mean a compound which, when added as a minor component to a main component, significantly increases the conductivity thereof.

p-Dopants known in the prior art are organic electron acceptor compounds, for example 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (F4TCNQ). The prior art further discloses, as p-dopants, metal complexes of transition metal cations and main group metal cations, for example in WO 2011/33023 and WO 2013/182389.

The hole transport materials known in the prior art and the p-dopants known in the prior art result in a great variety of potentially possible combinations. Of these, only a few are disclosed in the prior art. Mention may be made here by way of example of the combination of main group metal complexes as p-dopants with tetraamines, for example 2,2′,7,7′-tetra(N,N-di-p-tolyl)amino-9,9-spirobifluorene in the hole transport layer of an OLED. This is disclosed in WO 2013/182389. A further example from the prior art is the combination of F4TCNQ with monoarylamines, for example tris-para-biphenylamine in the hole transport layer of an OLED. This is disclosed in WO 2013/135352.

However, OLEDs comprising these materials in the hole transport layer are in need of improvement in relation to lifetime and efficiency.

There is additionally a need for p-dopants capable of efficiently doping hole transport materials having a low-lying HOMO, especially those having a HOMO within the range from −5.0 to −5.4 eV, such that it is possible to obtain dopant-hole transport material combinations having both a suitable conductivity and a low HOMO energy level. HOMO energies are determined here by the method specified in the working examples. Suitable and preferred conductivities are in the range from 10⁻⁴ S/m to 10⁻³ S/m, determined by the method specified in the working examples. The use of hole transport materials having a low-lying HOMO is highly desirable because this dispenses with the necessity of inserting a further layer having a low HOMO between hole transport layer and emitting layer. This enables a simpler construction of the OLED and hence a more efficient production process. If a further layer is inserted between hole transport layer and emitting layer, it is possible in the desired case of a hole transport layer having a low HOMO to avoid a hole barrier and hence a voltage drop between the hole transport layer and the emitting layer by virtue of the HOMO of the hole transport layer being no higher than the HOMO of the layer between the hole transport layer and emitting layer. This is possible, for example, through the use of the same material in the hole transport layer and the further layer between the hole transport layer and emitting layer.

There is additionally a need for hole transport material-dopant combinations having only a low absorption in the visible region (VIS region). The p-dopants known in the prior art, for example NDP-2 (commercially available from Novaled AG) or molybdenum oxide dopants, in combination with the standard hole transport materials have absorptions in the VIS region. The absence of significant absorption bands in the VIS region is highly desirable since absorptions in the VIS region affect the emission characteristics of the OLEDs and worsen the efficiency thereof.

In studies of possible combinations of p-dopants and hole transport materials for use in hole transport layers, it has now been found that, unexpectedly, a material comprising a monoarylamine of a specific formula (A) and a bismuth complex gives excellent values compared to the prior art in relation to lifetime and efficiency. In addition, the inventive material has lower leakage currents when used in OLEDs than materials according to the prior art. Without being bound to this theory, this may be caused by a lower lateral conductivity of the doped layer of the OLED. With pixels in displays becoming ever smaller, leakage currents are a great problem since they can lead to crosstalk between the pixels. The avoidance thereof is therefore desirable. Yet another feature of the inventive material is only a low absorption band in the VIS region. Yet another feature is that it is possible with the inventive material, because of the low HOMO position of the monoarylamine, to produce OLEDs which need not have any additional layer between the hole transport layer comprising the inventive material and the emitting layer and can therefore be produced in a more efficient manner.

The present application therefore provides a material comprising a compound A of a formula (A)

where the variables that occur are:

-   Z is CR¹; -   Ar¹ is the same or different at each instance and is an aromatic     ring system which has 6 to 30 aromatic ring atoms and may be     substituted by one or more R¹ radicals, or a heteroaromatic ring     system which has 5 to 30 aromatic ring atoms and may be substituted     by one or more R¹ radicals; -   R¹ is the same or different at each instance and is selected from H,     D, F, C(═O)R², CN, Si(R²)₃, P(═O)(R²)₂, OR², S(═O)R², S(═O)₂R²,     straight-chain alkyl or alkoxy groups having 1 to 20 carbon atoms,     branched or cyclic alkyl or alkoxy groups having 3 to 20 carbon     atoms, alkenyl or alkynyl groups having 2 to 20 carbon atoms,     aromatic ring systems having 6 to 30 aromatic ring atoms, and     heteroaromatic ring systems having 5 to 30 aromatic ring atoms;     where two or more R¹ radicals may be joined to one another and may     form a ring; where the alkyl, alkoxy, alkenyl and alkynyl groups     mentioned and the aromatic ring systems and heteroaromatic ring     systems mentioned may each be substituted by one or more R²     radicals; and where one or more CH₂ groups in the alkyl, alkoxy,     alkenyl and alkynyl groups mentioned may be replaced by —R²C═CR²—,     Si(R²)₂, C═O, C═NR², —C(═O)O—, —C(═O)NR²—, P(═O)(R²), —O—, —S—, SO     or SO₂; -   R² is the same or different at each instance and is selected from H,     D, F, CN, alkyl groups having 1 to 20 carbon atoms, aromatic ring     systems having 6 to 30 aromatic ring atoms and heteroaromatic ring     systems having 5 to 30 aromatic ring atoms; where two or more R²     radicals may be joined to one another and may form a ring; and where     the alkyl groups, aromatic ring systems and heteroaromatic ring     systems mentioned may be substituted by F or ON;     and a compound P which is a complex of bismuth.

A BRIEF DESCRIPTION OF THE FIGURE

The FIGURE illustrates the values obtained for the specific conductivity against the proportion by volume of the dopant, in each case for the following host/dopant combinations: i) BipFBz (=BiC1): DA1; ii) BipFBz (=BiC1): MA1; iii) BiC: DA1; and iv) BiC: MA1. Inventive combinations are ii) and iv).

An aromatic ring system in the context of this invention contains 6 to 60 carbon atoms in the ring system. It does not comprise any heteroatoms as aromatic ring atoms. An aromatic ring system in the context of this invention therefore does not contain any heteroaryl groups. An aromatic ring system in the context of this invention shall be understood to mean a system which does not necessarily contain only aryl groups but in which it is also possible for a plurality of aryl groups to be bonded by a single bond or by a non-aromatic unit, for example one or more optionally substituted C, Si, N, O or S atoms. In this case, the nonaromatic unit comprises preferably less than 10% of the atoms other than H, based on the total number of atoms other than H in the system. For example, systems such as 9,9′-spirobifluorene, 9,9′-diarylfluorene, triarylamine, diaryl ethers and stilbene are also to be regarded as aromatic ring systems in the context of this invention, and likewise systems in which two or more aryl groups are joined, for example, by a linear or cyclic alkyl, alkenyl or alkynyl group or by a silyl group. In addition, systems in which two or more aryl groups are joined to one another via single bonds are also to be regarded as aromatic ring systems in the context of this invention, for example systems such as biphenyl and terphenyl.

A heteroaromatic ring system in the context of this invention contains 5 to 60 aromatic ring atoms, at least one of which is a heteroatom. The heteroatoms of the heteroaromatic ring system are preferably selected from N, O and/or S. A heteroaromatic ring system corresponds to the abovementioned definition of an aromatic ring system, but has at least one heteroatom as one of the aromatic ring atoms. In this way, it differs from an aromatic ring system in the sense of the definition of the present application, which, according to this definition, cannot contain any heteroatom as aromatic ring atom.

An aryl group in the context of this invention contains 6 to 40 aromatic ring atoms of which none is a heteroatom. An aryl group in the context of this invention is understood to mean either a simple aromatic cycle, i.e. benzene, or a fused aromatic polycycle, for example naphthalene, phenanthrene or anthracene. A fused aromatic polycycle in the context of the present application consists of two or more simple aromatic cycles fused to one another. Fusion between cycles is understood here to mean that the cycles share at least one edge with one another.

A heteroaryl group in the context of this invention contains 5 to 40 aromatic ring atoms of which at least one is a heteroatom. The heteroatoms of the heteroaryl group are preferably selected from N, O and S. A heteroaryl group in the context of this invention is understood to mean either a simple heteroaromatic cycle, for example pyridine, pyrimidine or thiophene, or a fused heteroaromatic polycycle, for example quinoline or carbazole. A fused heteroaromatic polycycle in the context of the present application consists of two or more simple heteroaromatic cycles fused to one another. Fusion between cycles is understood to mean that the cycles share at least one edge with one another.

An aromatic ring system having 6 to 40 aromatic ring atoms or a heteroaromatic ring system having 5 to 40 aromatic ring atoms are especially understood to mean groups derived from the groups mentioned above under aryl groups and heteroaryl groups, and from biphenyl, terphenyl, quaterphenyl, fluorene, spirobifluorene, dihydrophenanthrene, dihydropyrene, tetrahydropyrene, indenofluorene, truxene, isotruxene, spirotruxene, spiroisotruxene, indenocarbazole, or from combinations of these groups.

An aryl or heteroaryl group, each of which may be substituted by the abovementioned radicals and which may be joined to the aromatic or heteroaromatic system via any desired positions, is especially understood to mean groups derived from benzene, naphthalene, anthracene, phenanthrene, pyrene, dihydropyrene, chrysene, perylene, triphenylene, fluoranthene, benzanthracene, benzophenanthrene, tetracene, pentacene, benzopyrene, furan, benzofuran, isobenzofuran, dibenzofuran, thiophene, benzothiophene, isobenzothiophene, dibenzothiophene, pyrrole, indole, isoindole, carbazole, pyridine, quinoline, isoquinoline, acridine, phenanthridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, phenothiazine, phenoxazine, pyrazole, indazole, imidazole, benzimidazole, naphthimidazole, phenanthrimidazole, pyndimidazole, pyrazinimidazole, quinoxalinimidazole, oxazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, benzothiazole, pyridazine, benzopyridazine, pyrimidine, benzopyrimidine, quinoxaline, pyrazine, phenazine, naphthyridine, azacarbazole, benzocarboline, phenanthroline, 1,2,3-triazole, 1,2,4-triazole, benzotriazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, tetrazole, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine, purine, pteridine, indolizine and benzothiadiazole.

In the context of the present invention, a straight-chain alkyl group having 1 to 20 carbon atoms and a branched or cyclic alkyl group having 3 to 20 carbon atoms and an alkenyl or alkynyl group having 2 to 20 carbon atoms in which individual hydrogen atoms or CH₂ groups may also be replaced by the groups mentioned above in the definition of the radicals are preferably understood to mean the methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, cyclopentyl, neopentyl, n-hexyl, cyclohexyl, neohexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, 2-ethylhexyl, trifluoromethyl, pentafluoroethyl, 2,2,2-trifluoroethyl, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, ethynyl, propynyl, butynyl, pentynyl, hexynyl or octynyl radicals.

An alkoxy or thioalkyl group having 1 to 20 carbon atoms in which individual hydrogen atoms or CH₂ groups may also be replaced by the groups mentioned above in the definition of the radicals is preferably understood to mean methoxy, trifluoromethoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, n-pentoxy, s-pentoxy, 2-methylbutoxy, n-hexoxy, cyclohexyloxy, n-heptoxy, cycloheptyloxy, n-octyloxy, cyclooctyloxy, 2-ethylhexyloxy, pentafluoroethoxy, 2,2,2-trifluoroethoxy, methylthio, ethylthio, n-propylthio, i-propylthio, n-butylthio, butylthio, s-butylthio, t-butylthio, n-pentylthio, s-pentylthio, n-hexylthio, cyclohexylthio, n-heptylthio, cycloheptylthio, n-octylthio, cyclooctylthio, 2-ethyl hexylthio, trifluoromethylthio, pentafluoroethylthio, 2,2,2-trifluoroethylthio, ethenylthio, propenylthio, butenylthio, pentenylthio, cyclopentenylthio, hexenylthio, cyclohexenylthio, heptenylthio, cycloheptenylthio, octenylthio, cyclooctenylthio, ethynylthio, propynylthio, butynylthio, pentynylthio, hexynylthio, heptynylthio or octynylthio.

The wording that two or more radicals together may form a ring, in the context of the present application, shall be understood to mean, inter alia, that the two radicals are joined to one another by a chemical bond. In addition, however, the abovementioned wording shall also be understood to mean that, if one of the two radicals is hydrogen, the second radical binds to the position to which the hydrogen atom was bonded, forming a ring.

The compound A preferably has a low-lying HOMO, more preferably a HOMO within the range from −5.0 to −5.4 eV, most preferably a HOMO within the range from −5.1 to −5.3 eV.

The compound A is a monoarylamine. A monoarylamine is understood here to mean a compound having a single arylamino group and not more than one. According to the invention, the compound A is a monotriarylamino compound, meaning that it has a single triarylamino group. The term “triarylamino group” is preferably also understood to mean compounds containing heteroaryl groups bonded to the amino nitrogen. Further preferably, the compound A has a single amino group. It should be noted that, according to the definition of the present application, carbazole groups do not count as arylamino groups or amino groups.

According to a further preferred embodiment of the invention, the compound A does not contain a fused aryl group having more than 10 aromatic ring atoms nor a fused heteroaryl group having more than 14 aromatic ring atoms.

Ar¹ is preferably the same or different at each instance and is an aromatic ring system which has 6 to 24 aromatic ring atoms and may be substituted by one or more R¹ radicals, or a heteroaromatic ring system which has 5 to 24 aromatic ring atoms and may be substituted by one or more R¹ radicals.

Preferably, at least one Ar¹ group in the compound of the formula (A) is a group which is optionally substituted by one or more R¹ radicals and is selected from phenyl, biphenyl, terphenyl, quaterphenyl, naphthyl, phenanthryl, fluoranthenyl, fluorenyl, indenofluorenyl, spirobifluorenyl, furanyl, benzofuranyl, isobenzofuranyl, dibenzofuranyl, thiophenyl, benzothiophenyl, isobenzothiophenyl, dibenzothiophenyl, indolyl, isoindolyl, carbazolyl, indolocarbazolyl, indenocarbazolyl, pyridyl, quinolinyl, isoquinolinyl, acridyl, phenanthridyl, benzimidazolyl, pyrimidyl, pyrazinyl and triazinyl; particular preference among these is given to phenyl, biphenyl, terphenyl, quaterphenyl, naphthyl, phenanthryl, fluoranthenyl, fluorenyl, indenofluorenyl, spirobifluorenyl, clibenzofuranyl, dibenzothiophenyl, carbazolyl, acridyl and phenanthridyl.

R¹ is preferably the same or different at each instance and is selected from H, D, F, CN, Si(R²)₃, straight-chain alkyl or alkoxy groups having 1 to 10 carbon atoms, branched or cyclic alkyl or alkoxy groups having 3 to 10 carbon atoms, aromatic ring systems having 6 to 40 aromatic ring atoms and heteroaromatic ring systems having 5 to 40 aromatic ring atoms; where the alkyl and alkoxy groups mentioned, the aromatic ring systems mentioned and the heteroaromatic ring systems mentioned may each be substituted by one or more R² radicals; and where one or more CH₂ groups in the alkyl or alkoxy groups mentioned may be replaced by —C≡C—, —R²C═CR²—, Si(R²)₂, C═O, C═NR², —O—, —S—, —C(═O)O— or —C(═O)NR²—.

R¹ is more preferably the same or different at each instance and is selected from H, F, CN, straight-chain alkyl or alkoxy groups having 1 to 8 carbon atoms, branched or cyclic alkyl or alkoxy groups having 3 to 8 carbon atoms, aromatic ring systems having 6 to 24 aromatic ring atoms, and heteroaromatic ring systems having 5 to 24 aromatic ring atoms, where said alkyl groups, said aromatic ring systems and said heteroaromatic ring systems may each be substituted by one or more R² radicals. Particular preference is given among these to H, F, methyl, ethyl, tert-butyl, and phenyl.

More preferably, the compound of the formula (A) contains no R¹ radical that is not H, exactly one R¹ radical that is not H, or exactly two R¹ radicals that are not H.

Preferably, at least one Ar¹ group, more preferably all the Ar¹ groups, in the compound of the formula (A) are the same or different at each instance and are selected from the following groups, each of which may be substituted by one or more R¹ radicals at any of the unsubstituted positions shown:

Preferred embodiments of compound A are the following compounds:

Preparation processes for-compounds of the formula (A) are known in the prior art. In particular, the person skilled in the art may make reference to the disclosure of document WO 2012/034627.

The compound P is a p-dopant in the sense of the abovementioned definition. Without being bound to this theory, it is assumed that the compound P is a Lewis acid which, when present mixed with the compound A, forms a complex with the compound A. The compound A acts here as a Lewis base. Without being bound to this theory, the complex is formed by virtue of a free electron pair in compound A interacting with the bismuth metal atom of compound P.

The compound P may be a mononuclear complex of bismuth, a binuclear complex of bismuth or a polynuclear complex of bismuth. It is possible that the compound P is a mononuclear complex of bismuth if it is present in the gas phase and a polynuclear complex of bismuth if it is in the solid phase. This means that the compound P may polymerize or depolymerize according to the state of matter.

The complex of bismuth is preferably a complex of bismuth in the (II), (Ill) or (V) oxidation state. It is more preferably a complex of bismuth in the (III) oxidation state.

Preferably, the complex of bismuth has at least one ligand L which is an organic compound. The ligand L is preferably selected from monodentate, bidentate and tridentate ligands, more preferably from monodentate ligands. Further preferably, the ligand L is negatively charged, preferably triply, doubly or singly negatively charged, more preferably singly negatively charged.

The group of the ligand L that binds to the bismuth atom is preferably selected from carboxylic acid groups, thiocarboxylic acid groups, in particular thiolic acid groups, thionic acid groups and dithiolic acid groups, carboxamide groups and carboximide groups, more preferably from carboxylic acid groups.

Preferably, the ligand L corresponds to one of the following formulae (L-I), (L-II), (L-III) and (L-IV)

where: W is selected from carboxylic acid groups; thiocarboxylic acid groups, in particular thiolic acid groups, thionic acid groups and dithiolic acid groups; carboxamide groups and carboximide groups, more preferably from carboxylic acid groups; U is the same or different at each instance and is selected from N and CR³ if no W group is bonded thereto, and U is C when a W group is bonded thereto; and R³ is the same or different at each instance and is selected from H, D, F, Cl, Br, I, CN, NO₂, CF₃, straight-chain alkyl or alkoxy groups having 1 to 20 carbon atoms, branched or cyclic alkyl or alkoxy groups having 3 to 20 carbon atoms, alkenyl or alkynyl groups having 2 to 20 carbon atoms, aromatic ring systems having 6 to 40 aromatic ring atoms, and heteroaromatic ring systems having 5 to 40 aromatic ring atoms; where the alkyl, alkoxy, alkenyl and alkynyl groups mentioned and the aromatic ring systems and heteroaromatic ring systems mentioned may each be substituted by one or more R⁴ radicals; and where one or more CH₂ groups in the alkyl, alkoxy, alkenyl and alkynyl groups mentioned may be replaced by —R⁴C═CR⁴—, —C≡C—, Si(R⁴)₂, C═O, C═NR⁴, —C(═O)O—, —C(═O)NR⁴—, P(═O)(R⁴), —O—, —S—, SO or SO₂; and R⁴ is the same or different at each instance and is selected from H, D, F, Cl, CN, NO₂, alkyl groups having 1 to 20 carbon atoms, aromatic ring systems having 6 to 40 aromatic ring atoms and heteroaromatic ring systems having 5 to 40 aromatic ring atoms; where two or more R⁴ radicals may be joined to one another and may form a ring; and where the alkyl groups, aromatic ring systems and heteroaromatic ring systems mentioned may be substituted by F, Cl, CN and NO₂; and R⁵ is the same or different at each instance and is selected from H, D, F, C(═O)R⁴, CN, Si(R⁴)₃, P(═O)(R⁴)₂, OR⁴, S(═O)R⁴, S(═O)₂R⁴, straight-chain alkyl or alkoxy groups having 1 to 20 carbon atoms, branched or cyclic alkyl or alkoxy groups having 3 to 20 carbon atoms, alkenyl or alkynyl groups having 2 to 20 carbon atoms, aromatic ring systems having 6 to 40 aromatic ring atoms, and heteroaromatic ring systems having 5 to 40 aromatic ring atoms; where two or more R¹ radicals may be joined to one another and may form a ring; where the alkyl, alkoxy, alkenyl and alkynyl groups mentioned and the aromatic ring systems and heteroaromatic ring systems mentioned may each be substituted by one or more R⁴ radicals; and where one or more CH₂ groups in the alkyl, alkoxy, alkenyl and alkynyl groups mentioned may be replaced by —R⁴C═CR⁴—, —C≡C—, Si(R⁴)₂, C═O, C═NR⁴, —C(═O)O—, —C(═O)NR⁴—, P(═O)(R⁴), —O—, —S—, SO or SO₂; and R⁶ is the same or different at each instance and is selected from H, D, F, Cl, Br, I, CN, NO₂, CF₃, straight-chain alkyl or alkoxy groups having 1 to 20 carbon atoms, branched or cyclic alkyl or alkoxy groups having 3 to 20 carbon atoms, alkenyl or alkynyl groups having 2 to 20 carbon atoms, aromatic ring systems having 6 to 40 aromatic ring atoms, and heteroaromatic ring systems having 5 to 40 aromatic ring atoms; where the alkyl, alkoxy, alkenyl and alkynyl groups mentioned and the aromatic ring systems and heteroaromatic ring systems mentioned may each be substituted by one or more R⁴ radicals; and where one or more CH₂ groups in the alkyl, alkoxy, alkenyl and alkynyl groups mentioned may be replaced by —R⁴C═CR⁴—, —C≡C—, Si(R⁴)₂, C═O, C═NR⁴, —C(═O)O—, —C(═O)NR⁴—, P(═O)(R⁴), —O—, —S—, SO or SO₂.

Preferably, in each of the formulae (L-I) to (L-III), at least one R³ group is present, selected from F, Cl, Br, I, CN, NO₂ and alkyl groups which have 1 to 20 carbon atoms and at least one substituent selected from F, Cl, CN and NO₂. Among the groups mentioned, particular preference is given to F, Cl, CN and CF₃.

More preferably, one, two, three, four or five R³ groups of this kind are present, even more preferably three, four or five, most preferably three or five.

Preferably, in formula (L-IV), at least one R⁶ group is present, selected from F, Cl, Br, I, CN, NO₂ and alkyl groups which have 1 to 20 carbon atoms and at least one substituent selected from F, Cl, CN and NO₂.

Among the groups mentioned, particular preference is given to F, Cl, CN and CF₃. More preferably, one, two or three R⁶ groups of this kind are present, most preferably three.

Preferred ligands L are selected from fluorinated benzoic acid derivatives, fluorinated or non-fluorinated phenylacetic acid derivatives and fluorinated or non-fluorinated acetic acid derivatives.

Examples of preferred fluorinated benzoic acid derivatives are: 2-(trifluoromethyl)benzoic acid; 3,5-difluorobenzoic acid; 3-hydroxy-2,4,6-triiodobenzoic acid; 3-fluoro-4-methylbenzoic acid; 3-(trifluoromethoxy)benzoic acid; 4-(trifluoromethoxy)benzoic acid; 4-chloro-2,5-difluorobenzoic acid; 2-chloro-4,5-difluorobenzoic acid; 2,4,5-trifluorobenzoic acid; 2-fluorobenzoic acid; 4-fluorobenzoic acid; 2,3,4-trifluorobenzoic acid; 2,3,5-trifluorobenzoic acid; 2,3-difluorobenzoic acid; 2,4-bis(trifluoromethyl)benzoic acid; 2,4-difluorobenzoic acid; 2,5-difluorobenzoic acid; 2,6-bis(trifluoromethyl)benzoic acid; 2,6-difluorobenzoic acid; 2-chloro-6-fluorobenzoic acid; 2-fluoro-4-(trifluoromethyl)benzoic acid; 2-fluoro-5-(trifluoromethyl)benzoic acid; 2-fluoro-6-(trifluoromethyl)benzoic acid; 3,4,5-trifluorobenzoic acid; 3,4-difluorobenzoic acid; 3,5-bis(trifluoromethyl)benzoic acid; 3-(trifluoromethyl)benzoic acid; 3-chloro-4-fluorobenzoic acid; 3-fluoro-5-(trifluoromethyl)benzoic acid; 3-fluorobenzoic acid; 4-fluoro-2-(trifluoromethyl)benzoic acid; 4-fluoro-3-(trifluoromethyl)benzoic acid; 5-fluoro-2-methylbenzoic acid; 2-(trifluoromethoxy)benzoic acid; 2,3,5-trichlorobenzoic acid; 4-(trifluoromethyl)benzoic acid; pentafluorobenzoic acid; and 2,3,4,5-tetrafluorobenzoic acid.

Examples of fluorinated or non-fluorinated phenylacetic acid derivatives are: 2-fluorophenylacetic acid; 3-fluorophenylacetic acid; 4-fluorophenylacetic acid; 2,3-difluorophenylacetic acid; 2,4-difluorophenylacetic acid; 2,6-difluorophenylacetic acid; 3,4-difluorophenylacetic acid; 3,5-difluorophenylacetic acid; pentafluoro-phenylacetic acid; 2-chloro-6-fluorophenylacetic acid; 2-chloro-3,6-difluorophenylacetic acid; 3-chloro-2,6-difluorophenylacetic acid; 3-chloro-4-fluorophenylacetic acid; 5-chloro-2-fluorophenylacetic acid; 2,3,4-trifluorophenylacetic acid; 2,3,5-trifluorophenylacetic acid; 2,3,6-trifluorophenylacetic acid; 2,4,5-trifluorophenylacetic acid; 2,4,6-trifluorophenylacetic acid; 3,4,5-trifluorophenylacetic acid; 3-chloro-2-fluorophenylacetic acid; 6-fluorophenylacetic acid; 4-chloro-2-fluorophenylacetic acid; 2-chloro-4-fluorophenylacetic acid.

Examples of fluorinated or non-fluorinated acetic acid derivatives are: difluoroacetic acid; trifluoroacetic acid; chlorodifluoroacetic acid; (3-chlorophenyl)difluoroacetic acid; (3,5-difluorophenyl)difluoroacetic acid; (4-butylphenyl) difluoroacetic acid; (4-tert-butylphenyl)difluoroacetic acid; (3,4-dimethyl phenyl)difluoroacetic acid; (3-chloro-4-fluorophenyl)-difluoroacetic acid; (4-chlorophenyl)-difluoroacetic acid; 2-biphenyl-3′,5′-difluoroacetic acid; 3-biphenyl-3′,5′-difluoroacetic acid; 4-biphenyl-3′,5′ difluoroacetic acid; 2-biphenyl-3′,4′-difluoroacetic acid; 3-biphenyl-3′,4′-difluoroacetic acid; 4-biphenyl-3′,4′-difluoroacetic acid and 2,2-difluoropropionic acid and higher homologues thereof.

The compounds mentioned in deprotonated form in the above list may also be present in protonated form in accordance with the invention. They are preferably in deprotonated form. The compounds mentioned in protonated form in the above list may also be present in deprotonated form, which is preferred in accordance with the invention.

The material of the invention may contain further compounds. It preferably contains essentially exclusively exactly one compound A and exactly one compound P. If further compounds are present, these are preferably compounds according to formula (A). In one possible embodiment of the invention, exactly two different compounds A and exactly one compound P are present in the material of the invention.

The compound P is preferably present as a dopant in the material of the invention. It is preferable that the material of the invention contains the compound P in a concentration of 0.1% to 30%, more preferably 0.5% to 25%, even more preferably 5% to 20%.

Percentages in the context of the present application are stated such that they mean % by volume in the case of gas phase deposition and % by weight in the case of application from the liquid phase.

The material of the invention is preferably in the form of a thin layer, more preferably of a functional layer of an electronic device. The present invention therefore also provides a layer, preferably a semiconductor layer, comprising the material of the invention.

The layer comprising the material of the invention preferably has a thickness of 1 to 500 nm, more preferably of 5 to 300 nm and most preferably of 8 to 250 nm. It is preferably used as hole-transporting layer in an electronic device, preferably of an OLED, as laid out in detail further down.

The layer comprising the material of the invention preferably has a specific conductivity between 10⁻² S/m and 10⁻⁵ S/m, more preferably between 10⁻³ S/m and 10⁻⁴ S/m, the latter being determined as specified in the working examples.

The material of the invention can be applied in the form of a layer from the gas phase, for example by means of the OVPD (organic vapour phase deposition) method or with the aid of carrier gas sublimation. In this case, the materials are applied at a pressure between 10⁻⁵ mbar and 1 bar. A special case of this method is the OVJP (organic vapour jet printing) method, in which the materials are applied directly by a nozzle and thus structured (for example M. S. Arnold et al., Appl. Phys. Lett. 2008, 92, 053301). Alternatively, the material can also be produced from the liquid phase, for example by spin-coating, or by any printing method, for example screen printing, flexographic printing, nozzle printing or offset printing, preferably LITI (light-induced thermal imaging, thermal transfer printing) or inkjet printing.

For the processing of the material of the invention from the liquid phase, for example by the abovementioned methods, formulations are required. These formulations may, for example, be solutions, dispersions or emulsions. For this purpose, it may be preferable to use mixtures of two or more solvents. Suitable and preferred solvents are, for example, toluene, anisole, o-, m- or p-xylene, methyl benzoate, mesitylene, tetralin, veratrole, THF, methyl-THF, THP, chlorobenzene, dioxane, phenoxytoluene, especially 3-phenoxytoluene, (−)-fenchone, 1,2,3,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene, 1-methylnaphthalene, 2-methylbenzothiazole, 2-phenoxyethanol, 2-pyrrolidinone, 3-methylanisole, 4-methylanisole, 3,4-dimethylanisole, 3,5-dimethylanisole, acetophenone, α-terpineol, benzothiazole, butyl benzoate, cumene, cyclohexanol, cyclohexanone, cyclohexylbenzene, decalin, dodecylbenzene, ethyl benzoate, indane, methyl benzoate, NMP, p-cymene, phenetole, 1,4-diisopropylbenzene, dibenzyl ether, diethylene glycol butyl methyl ether, triethylene glycol butyl methyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, diethylene glycol monobutyl ether, tripropylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 2-isopropyl naphthalene, pentylbenzene, hexylbenzene, heptylbenzene, octylbenzene, 1,1-bis(3,4-dimethylphenyl)ethane or mixtures of these solvents.

The invention therefore further provides a formulation, especially a solution, dispersion or emulsion, comprising the material of the invention and at least one solvent, preferably an organic solvent. The way in which such a formulation, especially such solutions, can be prepared is known to those skilled in the art and is described, for example, in WO 2002/072714, WO 2003/019694 and the literature cited therein.

In the case of gas phase deposition, both compound P and compound A are coevaporated, preferably from different vapour deposition sources, and deposited as a layer. In the case of application from the liquid phase, the compound P and the compound A are dissolved in solvent and then applied by means of the abovementioned printing techniques. The layer comprising the material of the invention is finally obtained by evaporating the solvent.

The present application therefore also provides a process for producing a layer comprising the material of the invention, characterized in that compound A and compound P are applied together from the gas phase, or in that a formulation comprising the material of the invention is applied from the liquid phase.

The material of the invention is suitable for use in electronic devices, preferably selected from the group consisting of organic electroluminescent devices (OLEDs), organic integrated circuits (OLECs), organic field-effect transistors (OFETs), organic thin-film transistors (OTFTs), organic light-emitting transistors (OLETs), organic solar cells (OSCs), organic optical detectors, organic photoreceptors, organic field-quench devices (OFQDs), organic light-emitting electrochemical cells (OLECs), and organic laser diodes (O-lasers).

This material may be used in different functions. Preference is given to the use of the material in a hole transport layer, especially in a hole injection layer, a hole transport layer, or an exciton blocker layer. The above-described use of the material likewise forms part of the subject-matter of the invention.

A hole transport layer according to the present application in a broader sense is a layer having a hole-transporting function between the anode and emitting layer. Specifically, a hole transport layer according to the present application is a layer which has a hole-transporting function, is present between the anode and emitting layer and is neither a hole injection layer nor an electron blocker layer nor an exciton blocker layer.

The invention further provides an electronic device comprising the material of the invention, preferably in the form of a layer. This electronic device is preferably selected from the abovementioned devices. More preferably, the electronic device is an OLED comprising anode, cathode and at least one emitting layer, characterized in that at least one layer, preferably a hole transport layer, comprises the material of the invention.

Apart from the cathode, anode and emitting layer, the OLED preferably comprises still further functional layers. These are selected, for example, from in each case one or more hole injection layers, hole transport layers, hole blocker layers, electron transport layers, electron injection layers, electron blocker layers, exciton blocker layers, interlayers, charge generation layers (IDMC 2003, Taiwan; Session 21 OLED (5), T. Matsumoto, T. Nakada, J. Endo, K. Mori, N. Kawamura, A. Yokoi, J. Kido, Multiphoton Organic EL Device Having Charge Generation Layer) and/or organic or inorganic p/n junctions.

The sequence of the layers of the OLED comprising the material of the invention is preferably as follows:

-   -   anode     -   hole injection layer     -   hole transport layer     -   optionally further hole transport layer     -   optionally electron blocker layer     -   emitting layer     -   optionally hole blocker layer     -   electron transport layer     -   electron injection layer     -   cathode.

However, it is not necessary for all the layers mentioned to be present, and further layers may additionally be present. It is preferable that the material of the invention, in the above layer sequence, is present in one or more layers selected from hole injection layer and hole transport layer, more preferably in a hole injection layer.

Particular preference is given to the following layer sequence:

-   -   anode     -   hole injection layer     -   hole transport layer     -   optionally electron blocker layer     -   emitting layer     -   electron transport layer     -   electron injection layer     -   cathode.

However, it is not necessary for all the layers mentioned to be present, and further layers may additionally be present. It is preferable that the material of the invention, in the above layer sequence, is present in one or more layers selected from hole injection layer and hole transport layer, more preferably in a hole injection layer.

The OLED of the invention may comprise several emitting layers. More preferably, these emission layers in this case have several emission maxima between 380 nm and 750 mm overall, such that the overall result is white emission; in other words, various emitting compounds which may fluoresce or phosphoresce and which emit blue, yellow, green, orange or red light are used in the emitting layers. Especially preferred are three-layer systems, i.e. systems having three emitting layers, where the three layers show blue, green and orange or red emission (for the basic construction see, for example, WO 2005/011013).

Preferably, the OLED comprises the material of the invention in a hole-transporting layer disposed between the anode and emitting layer, with one or more further layers preferably present between the layer comprising the material of the invention and the emitting layer. Preferably, these further layers are hole transport layers, more preferably electron blocker layers. The further layers mentioned may be p-doped or non-p-doped; preferably they are non-p-doped.

In a preferred embodiment of the invention, the HOMO levels of the hole-transporting layer (HTL) and the layer between the hole-transporting layer and emitting layer (EBL) meet the following condition: HOMO(HTL)<=HOMO(EBL).

In this way, it is possible to avoid a hole barrier and hence a voltage drop between the hole transport layer and the emitting layer. This is advantageously possible, for example, through the use of the same material in the hole transport layer and the further layer between the hole transport layer and emitting layer.

However, it may also be preferable that the material of the invention is disposed in a hole-transporting layer directly adjoining the emitting layer.

The hole transport layers disposed between the layer comprising the material of the invention and the emitting layer preferably comprise one or more identical or different compounds of the formula (A), preferably identical compounds of the formula (A). However, they may also comprise other compounds. In this case, said compounds are preferably selected from monoarylamines, as defined above.

It is further preferable that the OLED comprises the material of the invention in a layer directly adjoining the anode.

More preferably, the OLED of the invention comprises one of the following layer structures:

a) anode—layer comprising the material of the invention—electron blocker layer—emitting layer;

b) anode—layer comprising the material of the invention—hole transport layer—electron blocker layer—emitting layer;

c) anode—first layer comprising the material of the invention—hole transport layer—second layer comprising the material of the invention—electron blocker layer—emitting layer.

Those layers that preferably adjoin the emitting layer on the cathode side correspond to the abovementioned preferred layers in these positions, namely one or more hole blocker layers, electron transport layers and electron injection layers.

In structure a), it is possible for both the layer comprising the material of the invention and the electron blocker layer to comprise the same compound of the formula (A). In structure c), both the layer comprising the material of the invention and the hole transport layer may comprise the same compound of the formula (A) and/or both the second layer comprising the material of the invention and the electron blocker layer may comprise the same compound of the formula (A).

It is preferable when the material of the invention is used in an OLED comprising one or more phosphorescent emitting compounds. The term “phosphorescent emitting compounds” typically encompasses compounds where the emission of light is effected through a spin-forbidden transition, for example a transition from an excited triplet state or a state having a higher spin quantum number, for example a quintet state.

Suitable phosphorescent emitting compounds (triplet emitters) are especially compounds which, when suitably excited, emit light, preferably in the visible region, and also contain at least one atom of atomic number greater than 20, preferably greater than 38, and less than 84, more preferably greater than 56 and less than 80. Preferred phosphorescent emitting compounds are compounds containing copper, molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, gold or europium, especially compounds containing iridium, platinum or copper. In the context of the present invention, all luminescent iridium, platinum or copper complexes are considered to be phosphorescent emitting compounds.

Examples of the above-described emitting compounds can be found in applications WO 00/70655, WO 01/41512, WO 02/02714, WO 02/15645, EP 1191613, EP 1191612, EP 1191614, WO 05/033244, WO 05/019373 and US 2005/0258742. In general, all phosphorescent complexes as used for phosphorescent OLEDs according to the prior art and as known to those skilled in the art in the field of organic electroluminescent devices are suitable. It is also possible for the person skilled in the art, without exercising inventive skill, to use further phosphorescent complexes in combination with the material of the invention in an OLED

In an alternative embodiment, it is preferable that the material is used in an OLED comprising a fluorescent emitting compound in its emitting layer. Preferably, the emitting layer in this case comprises an arylamino compound as fluorescent emitting compound, more preferably in combination with a host material. The host material in this case is preferably selected from compounds comprising one or more anthracene groups.

Preferred embodiments of the different functional materials in the electronic device are listed hereinafter.

Preferred phosphorescent emitting compounds are the abovementioned compounds.

Preferred fluorescent emitting compounds are selected from the class of the arylamines. An arylamine or an aromatic amine in the context of this invention is understood to mean a compound containing three substituted or unsubstituted aromatic or heteroaromatic ring systems bonded directly to the nitrogen. Preferably, at least one of these aromatic or heteroaromatic ring systems is a fused ring system, more preferably having at least 14 aromatic ring atoms. Preferred examples of these are aromatic anthraceneamines, aromatic anthracenediamines, aromatic pyreneamines, aromatic pyrenediamines, aromatic chryseneamines or aromatic chrysenediamines. Further preferred emitting compounds are indenofluoreneamines or -diamines, for example according to WO 2006/108497 or WO 2006/122630, benzoindenofluoreneamines or -diamines, for example according to WO 2008/006449, and dibenzoindenofluoreneamines or -diamines, for example according to WO 2007/140847, and the indenofluorene derivatives having fused aryl groups disclosed in WO 2010/012328. Likewise preferred are the pyrenearylamines disclosed in WO 2012/048780 and in WO 2013/185871. Likewise preferred are the benzoindenofluoreneamines disclosed in WO 2014/037077, the benzofluoreneamines disclosed in WO 2014/106522 and the extended benzoindenofluorenes disclosed in WO 2014/111269.

Useful matrix materials, preferably for fluorescent emitting compounds, include materials of various substance classes. Preferred matrix materials are selected from the classes of the oligoarylenes (e.g. 2,2′,7,7′-tetraphenylspirobifluorene according to EP 676461 or dinaphthylanthracene), especially of the oligoarylenes containing fused aromatic groups, the oligoarylenevinylenes (e.g. DPVBi or spiro-DPVBi according to EP 676461), the polypodal metal complexes (for example according to WO 2004/081017), the hole-conducting compounds (for example according to WO 2004/058911), the electron-conducting compounds, especially ketones, phosphine oxides, sulphoxides, etc. (for example according to WO 2005/084081 and WO 2005/084082), the atropisomers (for example according to WO 2006/048268), the boronic acid derivatives (for example according to WO 2006/117052) or the benzanthracenes (for example according to WO 2008/145239). Particularly preferred matrix materials are selected from the classes of the oligoarylenes comprising naphthalene, anthracene, benzanthracene and/or pyrene or atropisomers of these compounds, the oligoarylenevinylenes, the ketones, the phosphine oxides and the sulphoxides. Very particularly preferred matrix materials are selected from the classes of the oligoarylenes comprising, anthracene, benzanthracene, benzophenanthrene and/or pyrene or atropisomers of these compounds. An oligoarylene in the context of this invention shall be understood to mean a compound in which at least three aryl or arylene groups are bonded to one another.

Preferred matrix materials for phosphorescent emitting compounds are aromatic ketones, aromatic phosphine oxides or aromatic sulphoxides or sulphones, for example according to WO 2004/013080, WO 2004/093207, WO 2006/005627 or WO 2010/006680, triarylamines, carbazole derivatives, e.g. CBP (N,N-biscarbazolylbiphenyl) or the carbazole derivatives disclosed in WO 2005/039246, US 2005/0069729, JP 2004/288381, EP 1205527 or WO 2008/086851, indolocarbazole derivatives, for example according to WO 2007/063754 or WO 2008/056746, indenocarbazole derivatives, for example according to WO 2010/136109, WO 2011/000455 or WO 2013/041176, azacarbazole derivatives, for example according to EP 1617710, EP 1617711, EP 1731584, JP 2005/347160, bipolar matrix materials, for example according to WO 2007/137725, silanes, for example according to WO 2005/111172, azaboroles or boronic esters, for example according to WO 2006/117052, triazine derivatives, for example according to WO 2010/015306, WO 2007/063754 or WO 2008/056746, zinc complexes, for example according to EP 652273 or WO 2009/062578, diazasilole or tetraazasilole derivatives, for example according to WO 2010/054729, diazaphosphole derivatives, for example according to WO 2010/054730, bridged carbazole derivatives, for example according to US 2009/0136779, WO 2010/050778, WO 2011/042107, WO 2011/088877 or WO 2012/143080, triphenylene derivatives, for example according to WO 2012/048781, or lactams, for example according to WO 2011/116865 or WO 2011/137951.

Suitable charge transport materials as usable in the hole injection or hole transport layer or electron blocker layer or in the electron transport layer of the electronic device of the invention are, as well as the compounds of the formula (A), for example, the compounds disclosed in Y. Shirota et al., Chem. Rev. 2007, 107(4), 953-1010, or other materials as used in these layers according to the prior art.

Examples of preferred materials which can be used in a hole transport, hole injection or electron blocker layer in the electroluminescent device of the invention are, as well as the compounds of the formula (A), indenofluorenamine derivatives (for example according to WO 06/122630 or WO 06/100896), the amine derivatives disclosed in EP 1661888, hexaazatriphenylene derivatives (for example according to WO 01/049806), amine derivatives having fused aromatic systems (for example according to U.S. Pat. No. 5,061,569), the amine derivatives disclosed in WO 95/09147, monobenzoindenofluoreneamines (for example according to WO 08/006449), dibenzoindenofluoreneamines (for example according to WO 07/140847), spirobifluoreneamines (for example according to WO 2012/034627 and WO 2013/120577), fluoreneamines (for example according to WO 2014/015937, WO 2014/015938 and WO 2014/015935), spirodibenzopyranamines (for example according to WO 2013/083216) and dihydroacridine derivatives (for example according to WO 2012/150001).

Materials used for the electron transport layer may be any materials as used according to the prior art as electron transport materials in the electron transport layer. Especially suitable are aluminium complexes, for example Alq₃, zirconium complexes, for example Zrq₄, lithium complexes, for example Liq, benzimidazole derivatives, triazine derivatives, pyrimidine derivatives, pyridine derivatives, pyrazine derivatives, quinoxaline derivatives, quinoline derivatives, oxadiazole derivatives, aromatic ketones, lactams, boranes, diazaphosphole derivatives and phosphine oxide derivatives.

Preferred cathodes of the electronic device are metals having a low work function, metal alloys or multilayer structures composed of various metals, for example alkaline earth metals, alkali metals, main group metals or lanthanoids (e.g. Ca, Ba, Mg, Al, In, Mg, Yb, Sm, etc.). Additionally suitable are alloys composed of an alkali metal or alkaline earth metal and silver, for example an alloy composed of magnesium and silver. In the case of multilayer structures, in addition to the metals mentioned, it is also possible to use further metals having a relatively high work function, for example Ag or Al, in which case combinations of the metals such as Ca/Ag, Mg/Ag or Ba/Ag, for example, are generally used. It may also be preferable to introduce a thin interlayer of a material having a high dielectric constant between a metallic cathode and the organic semiconductor. Examples of useful materials for this purpose are alkali metal or alkaline earth metal fluorides, but also the corresponding oxides or carbonates (e.g. LiF, Li₂O, BaF₂, MgO, NaF, CsF, Cs₂CO₃, etc.). It is also possible to use lithium quinolinate (LiQ) for this purpose. The layer thickness of this layer is preferably between 0.5 and 5 nm.

Preferred anodes are materials having a high work function. Preferably, the anode has a work function of greater than 4.5 eV versus vacuum. Firstly, metals having a high redox potential are suitable for this purpose, for example Ag, Pt or Au. On the other hand, metal/metal oxide electrodes (e.g. Al/Ni/NiO_(x), Al/PtO_(x)) may also be preferred. For some applications, at least one of the electrodes has to be transparent or partly transparent in order to enable the irradiation of the organic material (organic solar cell) or the emission of light (OLED, O-LASER). Preferred anode materials here are conductive mixed metal oxides. Particular preference is given to indium tin oxide (ITO) or indium zinc oxide (IZO). Preference is further given to conductive doped organic materials, especially conductive doped polymers. In addition, the anode may also consist of two or more layers, for example of an inner layer of ITO and an outer layer of a metal oxide, preferably tungsten oxide, molybdenum oxide or vanadium oxide.

The device is structured appropriately (according to the application), contact-connected and finally sealed, in order to rule out damaging effects by water and air.

In a preferred embodiment, the electronic device is characterized in that one or more layers are coated by a sublimation process. In this case, the materials are applied by vapour deposition in vacuum sublimation systems at an initial pressure of less than 10⁻⁵ mbar, preferably less than 10⁻⁶ mbar.

In this case, however, it is also possible that the initial pressure is even lower, for example less than 10⁻⁷ mbar. Preferred methods for application of layers from the gas phase are described further up, and apply generally to the production of layers in the OLEDs of the invention.

In an alternative embodiment, the electronic device is characterized in that one or more layers are applied from solution. Preferred methods for application of layers from solution are described further up, and apply generally to the production of layers in the OLEDs of the invention.

The OLEDs of the invention can be used in displays, as light sources in lighting applications and as light sources in medical and/or cosmetic applications (for example light therapy).

WORKING EXAMPLES A) Syntheses

1) Synthesis of BiC

50 g (113.56 mmol) of triphenylbismuthane (CAS No.: 603-33-8) and 89.40 g of 3,5-bis(trifluoromethyl)benzoic acid (340.36 mmol) are initially charged in a flask inertized under argon and 1 l of dried toluene is added. The mixture is heated gradually to 80° C. and then stirred at this temperature for a further 12 hours. The mixture is subsequently cooled to room temperature and filtered through a protective gas frit, washed three times with toluene, dried at the vacuum pump and then sublimed under high vacuum.

2) Synthesis of bismuth tris(pentafluorobenzoate) Bi[OOC—C₆F₅]₃ (BipFBz=BiC1)

The synthesis proceeds analogously to the above synthesis, with corresponding use of pentafluorobenzoic acid as ligand rather than 3,5-bis-(trifluoromethyl)benzoic acid.

B) Conductivity Measurements

The compounds DA1 and MA1 are each coevaporated with one of the dopants BiC and BipFBz (for structures see Table 2 below) in proportions by volume between 1% by volume and 15% by volume. This produces different layer thicknesses.

Subsequently, the specific conductivities of the layers are measured. For this purpose, the following method is used:

The conductivity of the doped layers is determined by means of what is called a finger structure. This involves two intermeshing structured ITO electrodes shaped like fingers. Between the finger electrodes is the (doped) organic layer having a thickness d. The gap width between the electrodes has the value S. A safety margin between the supply and the ITO electrodes ensures that the current measured results from the current flow between the ITO fingers. I(U) (current-voltage characteristic) is measured for various values of S (typically a few μm) and d (typically 120 nm). From this, it is possible to unambiguously determine the conductivity of doped layers by the following formula:

$\sigma = {\frac{I}{L \cdot d} \cdot \frac{S}{U}}$

The advantage of this method over a metal-doped layer/ITO construction is that the ohmic behaviour is extended over a wide voltage range and the two contacts consist of the same material, such that the barrier heights for charge carrier injection between contact and organic are identical in forward and reverse direction. The values obtained for the specific conductivity are plotted in the FIGURE against the proportion by volume of the dopant, in each case for the following host/dopant combinations: i) BipFBz (=BiC1): DA1; ii) BipFBz (=BiC1): MA1; iii) BiC: DA1; and iv) BiC: MA1. Inventive combinations are ii) and iv).

It is found that the desired specific conductivities of between 10⁻⁴ S/m and 10⁻³ S/m, in the inventive cases, can be achieved within a wide range between 5% and 14% by volume. Dopant concentrations in the range between 5% and 14% by volume are practical and can be established easily.

A particular advantage of the inventive Bi dopants BiC and BipFBz is that it is thus possible to dope not only hole transport materials having a high-lying HOMO, such as DA1 (HOMO about −4.83 eV) but also hole transport materials having a low-lying HOMO such as MA1 (HOMO about −5.18 eV) to the desired specific conductivity (see combinations ii) and iv) above with the hole transport material MA1). The use of hole transport materials with a low-lying HOMO is highly desirable because this dispenses with the necessity of inserting a further layer having a low HOMO between the hole transport layer and emitting layer. This enables a simpler construction of the OLED and hence a more efficient production process.

C) Measurement of the Absorption Properties of the Dopants of the Invention

The host/dopant combinations ii) and iv) specified in B) and the NDP-2:NHT-5 combination (2% by volume of NDP-2) according to the prior art are analysed for their absorption in the VIS range. It is found that the inventive combinations comprising Bi dopants have only a low absorption in the VIS range. In contrast, for the combination of materials NHT-5 and NDP-2 according to prior art, an absorption band is observed in the visible region with an absorption maximum at about 500 nm. The absence of significant absorption bands in the visible region is an important use advantage of the inventive combinations of hole transport materials with Bi dopants. Absorptions in the VIS range affect the emission characteristics of the OLED and worsen the efficiency thereof.

D) Device Examples

In examples I1 to 14 and C1 to C4 which follow, the data of various OLEDs are presented. Examples C1 to C4 are comparative examples according to the prior art; examples I1 to I4 show data of OLEDs of the invention.

OLEDs of the invention and OLEDs according to the prior art are produced by a general method according to WO 2004/058911, which is adapted to the circumstances described here (variation in layer thickness, materials). Glass plaques which have been coated with structured ITO (indium tin oxide) in a thickness of 50 nm are the substrates for the OLEDs. The substrates are subjected to wet cleaning (cleaning machine, detergent: Merck Extran), then baked at 250° C. for 15 min and, prior to the coating, treated with an oxygen plasma.

Various layers are applied to the pretreated substrates: first hole transport layer (HTL1)/second hole transport layer (HTL2)/optional third hole transport layer (HTL3)/emission layer (EML)/electron transport layer (ETL)/electron injection layer (EIL) and finally a 100 nm-thick aluminium cathode. The exact structure of the OLEDs can be found in Table 1. The materials used for production of the OLEDs are shown in Table 2.

All materials are applied by thermal vapour deposition in a vacuum chamber. In this case, the emission layer always consists of at least one matrix material and an emitting compound which is added to the matrix material(s) in a particular proportion by volume by co-evaporation. Details given in such a form as M1:D1 (95%:5%) mean here that the material M1 is present in the layer in a proportion by volume of 95% and D1 in a proportion by volume of 5%. Analogously, the electron transport layer may also consist of a mixture of two materials.

The OLEDs are characterized in a standard manner. For this purpose, the electroluminescence spectra and the external quantum efficiency (EQE, measured in percent) are determined as a function of luminance, calculated from current-voltage-luminance characteristics (IUL characteristics) assuming Lambertian radiation characteristics, and the lifetime. The electroluminescence spectra are determined at a luminance of 1000 cd/m², and the CIE 1931 x and y color coordinates are calculated therefrom. The lifetime LT80 is defined as the time after which the luminance drops from the starting luminance to 80% of the start value in the course of operation with constant current density.

TABLE 1 Structure of the OLEDs HTL1 HTL2 HTL3 EML ETL EIL Ex. thickness thickness thickness thickness thickness thickness C1 MA1: MA1: MA1 M1:D1 ST1:LiQ LiQ F4TCNQ F4TCNQ 20 nm (95%:5%) (50%:50%) 1 nm (95%:5%) (95%:5%) 20 nm 30 nm 20 nm 155 nm C2 MA1: MA1 MA1 M1:D1 ST1:LiQ LiQ F4TCNQ 155 nm 20 nm (95%:5%) (50%:50%) 1 nm (95%:5%) 20 nm 30 nm 20 nm C3 NPB:BiC NPB M1:D1 ST1:LiQ LiQ (95%:5%) 180 NM (95%:5%) (50%:50%) 1 nm 20 nm 20 nm 30 nm C4 DA1:BiC DA2 M1:D1 ST1:LiQ LiQ (95%:5%) 180 nm (95%:5%) (50%:50%) 1 nm 20 nm 20 nm 30 nm I1 MA1:BiC MA1:BiC MA1 M1:D1 ST1:LiQ LiQ (95%:5%) (95%:5%) 20 nm (95%:5%) (50%.50%) 1 nm 20 nm 155 nm 20 nm 30 nm I2 MA1:B1C MA1 MA1 M1:D1 ST1:LiQ LiQ (95%:5%) 155 nm 20 nm (95%:5%) (50%:50%) 1 nm 20 nm 20 nm 30 nm I3 MA1:BiC MA1 M1:D1 ST1:LiQ LiQ (95%:5%) 180 nm (95%:5%) (50%:50%) 1 nm 20 nm 20 nm 30 nm I4 MA3:BiC MA3 M1:D1 ST1:LiQ LiQ (95%:5%) 180 nm (95%:5%) (50%:50%) 1 nm 20 nm 20 nm 30 nm

TABLE 2 Structural formulae of the materials for the OLEDs

Commercially available (Novaled) NDP-2 Commercially available (Novaled) NHT-5

The examples are elucidated in detail hereinafter, in order to illustrate the advantages of the OLEDs of the invention.

Example 1

Inventive sample I1 is compared with comparative sample C1. The former differs from C1 in that it contains the p-dopant BiC rather than the p-dopant F4TCNQ in HTL1 and HTL2. Comparison of I1 and C1 shows a much lower leakage current at an applied voltage of 1 V of 7.9 E-6 mA/cm² compared to 1.6 E-4 mA/cm² with the present sample geometry and a pixel size of 2×2 mm². Leakage currents are understood to mean current flows between the anode and cathode which do not flow through the organic layers of the OLED. One of their causes may be a high lateral conductivity in the p-doped layer of the OLED. Leakage currents are a great problem with decreasing pixel size in displays, since they can lead to crosstalk between the pixels.

Example 2

Inventive sample I2 is compared with comparative sample C2. The former differs from C2 in that it contains the p-dopant BiC rather than the p-dopant F4TCNQ in HTL1. Comparison of 12 and C2 shows a comparable voltage of the two samples of 3.8 V @ 10 mA/cm². However, the efficiency is much higher in the case of 12 (8.9% EQE @ 10 mA/cm²) as compared with the comparative sample C2 (8.5% EQE @ 10 mA/cm²). The lifetime of the two samples is about 300 h LT80 @ 60 mA/cm².

Example 3

Inventive sample I4 is compared with comparative samples C3 and C4. The former differs from C3 and C4 in that it contains a specific compound of formula (A) as material for the HTL, and not the hole-transporting compounds known from the prior art. The p-dopant BiC is always used in the first of the two hole-transporting layers present. Inventive sample I4 has a better lifetime and efficiency than the comparative samples C3 and C4 (Table 3), with similar values for voltage.

TABLE 3 Results for the OLEDs Ex. U @ 10 mA/cm² EQE @ 10 mA/cm² LT80 @ 60 mA/cm² C3 4.3 5.7 195 C4 3.8 4.1 50 I4 4.1 8.1 355

The examples shown illustrate the advantages of the inventive combination of bismuth complexes with compounds of the formula (A) as hole transport materials in OLEDs. They should not be interpreted in a restrictive manner. The advantages of the inventive combination extend over the whole scope of the material combinations defined in the claims.

E) Quantum-Chemical Method for Determination of Orbital Energies

The HOMO and LUMO energies of the materials are determined via quantum-chemical calculations. In this present case, the software package “Gaussian09, Revision D.01” (Gaussian Inc.) is used. For calculation of organic substances without metals (referred to as the “org.” method), a geometry optimization is first conducted by the semi-empirical method AM1 (Gaussian input line “# AM1 opt”) with charge 0 and multiplicity 1. Subsequently, on the basis of the optimized geometry, a single-point energy calculation is effected for the electronic ground state and the triplet level. This is done using the TDDFT (time dependent density functional theory) method B3PW91 with the 6-31G(d) basis set (Gaussian input line “# B3PW91/6-31G(d) td=(50-50,nstates=4)”) (charge 0, multiplicity 1). For organometallic compounds (referred to as the “M-org.” method), the geometry is optimized by the Hartree-Fock method and the LanL2 MB basis set (Gaussian input line “# HF/LanL2 MB opt”) (charge 0, multiplicity 1). The energy calculation is effected, as described above, analogously to that for the organic substances, except that the “LanL2DZ” basis set is used for the metal atom and the “6-31G(d)” basis set for the ligands (Gaussian input line “#B3PW91/gen pseudo=lanl2 td=(50−50,nstates=4)”). From the energy calculation, the HOMO is obtained as the last orbital occupied by two electrons (alpha occ. eigenvalues) and LUMO as the first unoccupied orbital (alpha virt. eigenvalues) in Hartree units, where HEh and LEh represent the HOMO energy in Hartree units and the LUMO energy in Hartree units respectively. This is used to calculate the HOMO and LUMO value in electron volts, calibrated by cyclic voltammetry measurements, as follows: HOMO(eV)=((HEh*27.212)−0.9899)/1.1206 LUMO(eV)=((LEh*27.212)−2.0041)/1.385

These values are to be regarded as HOMO and as LUMO of the materials in the context of this application.

The method described herein is independent of the software package used and always gives the same results. Examples of frequently utilized programs for this purpose are “Gaussian09” (Gaussian Inc.) and Q-Chem 4.1 (Q-Chem, Inc.). In the present case, the energies are calculated using the software package “Gaussian09, Revision D.01”. 

The invention claimed is:
 1. A material comprising a compound A of a formula (A)

where the variables that occur are: Z is CR¹; Ar¹ is the same or different at each instance and is an aromatic ring system which has 6 to 24 aromatic ring atoms and is optionally substituted by one or more R¹ radicals, or a heteroaromatic ring system which has 5 to 24 aromatic ring atoms and is optionally substituted by one or more R¹ radicals; R¹ is the same or different at each instance and is selected from H, D, F, C(═O)R², CN, Si(R²)₃, P(═O)(R²)₂, OR², S(═O)R², S(═O)₂R², straight-chain alkyl or alkoxy groups having 1 to 20 carbon atoms, branched or cyclic alkyl or alkoxy groups having 3 to 20 carbon atoms, alkenyl or alkynyl groups having 2 to 20 carbon atoms, aromatic ring systems having 6 to 30 aromatic ring atoms, and heteroaromatic ring systems having 5 to 30 aromatic ring atoms; where two or more R¹ radicals is optionally joined to one another and may form a ring; where the alkyl, alkoxy, alkenyl and alkynyl groups mentioned and the aromatic ring systems and heteroaromatic ring systems mentioned may each be substituted by one or more R² radicals; and where one or more CH₂ groups in the alkyl, alkoxy, alkenyl and alkynyl groups mentioned is optionally replaced by —R²C═CR²—, —C≡C—, Si(R²)₂, C═O, C═NR², —C(═O)O—, —C(═O)NR²—, P(═O)(R²), —O—, —S—, SO or SO₂; R² is the same or different at each instance and is selected from H, D, F, CN, alkyl groups having 1 to 20 carbon atoms, aromatic ring systems having 6 to 30 aromatic ring atoms and heteroaromatic ring systems having 5 to 30 aromatic ring atoms; where two or more R² radicals is optionally joined to one another and may form a ring; and where the alkyl groups, aromatic ring systems and heteroaromatic ring systems mentioned is optionally substituted by F or CN; and a compound P which is a complex of bismuth.
 2. The material according to claim 1, wherein the compound A does not contain a fused aryl group having more than 10 aromatic ring atoms nor a fused heteroaryl group having more than 14 aromatic ring atoms.
 3. The material according to claim 1, wherein, in the compound A, the Ar¹ group is a group which is optionally substituted by one or more R¹ radicals and is selected from the group consisting of phenyl, biphenyl, terphenyl, quaterphenyl, naphthyl, phenanthryl, fluoranthenyl, fluorenyl, indenofluorenyl, spirobifluorenyl, dibenzofuranyl, dibenzothiophenyl, carbazolyl, acridyl and phenanthridyl.
 4. The material according to claim 1, wherein the compound P is a complex of bismuth in the (III) oxidation state.
 5. The material according to claim 1, wherein the compound P is a complex of bismuth having at least one ligand L which is an organic compound.
 6. The material according to claim 5, wherein the ligand L is singly negatively charged.
 7. The material according to claim 5, wherein the group in the ligand L that binds to the bismuth atom is selected from the group consisting of carboxylic acid groups, thiocarboxylic acid groups, carboxamide groups and carboximide groups.
 8. The material according to claim 5, wherein the ligand L is selected from fluorinated benzoic acid derivatives, fluorinated or non-fluorinated phenylacetic acid derivatives and fluorinated or non-fluorinated acetic acid derivatives.
 9. The material according to claim 1, wherein the compound P is present in the material as a dopant in a concentration of 0.1% to 30%.
 10. A layer for use in an electronic device, comprising the material according to claim
 1. 11. A formulation comprising the material according to claim 1 and at least one solvent.
 12. A process for producing a layer according to claim 10, which comprises applying compound A and compound P together from the gas phase.
 13. A process for producing a layer which comprises applying a formulation comprising the material according to claim 1 and a solvent from the liquid phase.
 14. An electronic device selected from organic electroluminescent devices, organic integrated circuits, organic field-effect transistors, organic thin-film transistors, organic light-emitting transistors, organic solar cells, organic optical detectors, organic photoreceptors, organic field-quench devices, organic light-emitting electrochemical cells and organic laser diodes, comprising a material according to claim
 1. 15. The device according to claim 14, wherein the device is an organic electroluminescent device wherein the device includes the material in a hole-transporting layer disposed between anode and emitting layer, with one or more further layers present between the layer comprising the material and the emitting layer.
 16. The organic electroluminescent device according to claim 15, wherein the HOMO levels of the hole-transporting layer (HTL) and the one layer between hole-transporting layer and emitting layer (EBL) meet the following condition: HOMO(HTL)<=HOMO(EBL).
 17. The organic electroluminescent device according to claim 15, wherein the one or more further layers disposed between the layer comprising the material and the emitting layer comprise one or more identical or different compounds of the formula (A).
 18. The device according to claim 14, wherein the device is an organic electroluminescent device wherein the device comprises the material in a layer directly adjoining the anode.
 19. The material according to claim 1, wherein R¹ is the same or different at each instance and is selected from H, F, CN, straight-chain alkyl or alkoxy groups having 1 to 8 carbon atoms, branched or cyclic alkyl or alkoxy groups having 3 to 8 carbon atoms, aromatic ring systems having 6 to 24 aromatic ring atoms, and heteroaromatic ring systems having 5 to 24 aromatic ring atoms, where said alkyl groups, said aromatic ring systems and said heteroaromatic ring systems may each be substituted by one or more R² radicals and R² is the same or different at each instance and is selected from H, D, F, CN, alkyl groups having 1 to 20 carbon atoms, aromatic ring systems having 6 to 30 aromatic ring atoms and heteroaromatic ring systems having 5 to 30 aromatic ring atoms.
 20. The material according to claim 1, wherein the compound P is a complex of bismuth in the (III) oxidation state and is a complex of bismuth having at least one ligand L, wherein the group in the ligand L that binds to the bismuth atom which is an organic compound and is selected from the group consisting of carboxylic acid groups, thiocarboxylic acid groups, carboxamide groups and carboximide groups.
 21. The material according to claim 19, wherein the compound P is a complex of bismuth in the (III) oxidation state and is a complex of bismuth having at least one ligand L, wherein the group in the ligand L that binds to the bismuth atom is which is an organic compound and is selected from the group consisting of carboxylic acid groups, thiocarboxylic acid groups, carboxamide groups and carboximide groups.
 22. An organic electroluminescent device comprising a hole transporting layer, comprising the material according to claim
 1. 23. The organic electroluminescent device according to claim 22, wherein R¹ is the same or different at each instance and is selected from H, F, CN, straight-chain alkyl or alkoxy groups having 1 to 8 carbon atoms, branched or cyclic alkyl or alkoxy groups having 3 to 8 carbon atoms, aromatic ring systems having 6 to 24 aromatic ring atoms, and heteroaromatic ring systems having 5 to 24 aromatic ring atoms, where said alkyl groups, said aromatic ring systems and said heteroaromatic ring systems may each be substituted by one or more R² radicals and R² is the same or different at each instance and is selected from H, D, F, CN, alkyl groups having 1 to 20 carbon atoms, aromatic ring systems having 6 to 30 aromatic ring atoms and heteroaromatic ring systems having 5 to 30 aromatic ring atoms.
 24. The organic electroluminescent device according to claim 22, wherein the compound P is a complex of bismuth in the (III) oxidation state and is a complex of bismuth having at least one ligand L, wherein the group in the ligand L that binds to the bismuth atom which is an organic compound and is selected from the group consisting of carboxylic acid groups, thiocarboxylic acid groups, carboxamide groups and carboximide groups.
 25. The organic electroluminescent device according to claim 23, wherein the compound P is a complex of bismuth in the (III) oxidation state and is a complex of bismuth having at least one ligand L, wherein the group in the ligand L that binds to the bismuth atom is which is an organic compound and is selected from the group consisting of carboxylic acid groups, thiocarboxylic acid groups, carboxamide groups and carboximide groups. 